Objective: Acoustic radiation force impulse imaging (ARFI) is a non-invasive method for the quantification of liver stiffness. We aimed to develop standards for the measuring procedure and studied the impact of different measuring sites.
Materials and methods: ARFI was tested in a tissue phantom and in 50 healthy volunteers. In addition, 116 patients with chronic liver disease underwent ARFI. The results were compared with histological staging (non-viral liver disease) and transient elastography (hepatitis C). ARFI diagnostic performance was evaluated with receiver operating characteristic curves.
Results: ARFI results were not normally distributed in >20% of cases. Deep inspiration significantly increased ARFI values by 13% (p < 0.05). The mean shear-wave velocity in healthy individuals was 1.28 ± 0.19 m/s in the left liver lobe and 1.15 ± 0.17 m/s in the right liver lobe (p < 0.001). Similarly, in 79/116 patients with chronic liver disease a significant difference of shear-wave velocity between both liver lobes was detected. The histological staging correlated with ARFI results of the biopsy site (r = 0.661, p < 0.001) in non-viral liver disease (n = 47). The mean shear-wave velocity in cases with F1 and F2 fibrosis was increased in the left compared with the right liver lobe (2.1 ± 0.73 m/s vs. 1.75 ± 0.89 m/s, p = 0.041). Similar results were obtained in patients with hepatitis C (n = 69).
Conclusion: Our study strengthens the necessity for definition of examination standards and demonstrates the usefulness of ARFI in non-viral liver disease. Interlobe variations of liver stiffness demand further investigation.